The paper presents the evolution of solar
and geomagnetic conditions, galactic cosmic ray flux, and solar energetic
particle occurrences from one sunspot minima to another starting from Maunder
minimum period up to the recent long deep minimum between solar cycles 23 and
24. The study seems to confirm the Gleissberg periodicity of 90-100 years for
the occurrence of long deep solar minimum and long term trends in these
parameters. Their implications on the earth’s ionosphere are discussed in this
paper. In addition, possible ionospheric effects of weak geomagnetic
disturbances, large proton events, lightning and seismic phenomena occurring
during the deep solar minima epochs are discussed.

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